Turbine systems employ a pressurized gas to provide mechanical energy to blades of a rotor. As the pressurized gas is expanded in a turbine, the rotor generates mechanical energy in the form of torque on a shaft of the rotor. Common gases used in turbine systems include atmospheric air (mainly nitrogen) and steam (H.sub.2 O).
An example of a prior art open, atmospheric air, combustion turbine 120 is shown in FIG. 1. The turbine 120 shown in FIG. 1 has an eight stage axial compressor 124 and 126, combustor 128, and three stage axial flow turbine component 134. In this turbine 120, atmospheric air is drawn in an air inlet 122 and compressed by the stator blades 124 and compressor blades 126. The air (or gas) generated by the compressor blades 126 has increased pressure and temperature and lower volume as compared to the gas which entered the compressor. This gas is further heated or super heated in the combustor 128 where fuel is added at the fuel inlet 132. The gas generated by the combustor 128 has increased volume and temperature as compared to the gas which entered the combustor.
The high pressure, high temperature gas generated by the combustor 128 is passed along blades of the turbine component 134 causing rotation of the shaft 138 of the turbine and the generation of energy. Then the gas passes into the turbine exhaust 136. The gas which exits past the blades of the turbine component 134 has lower pressure and temperature and increased volume as compared to the gas which exited the combustor 128. The exhaust gas, however, still has increased temperature and volume as compared to the atmospheric air which initially entered the air inlet 122.
Semi-closed and closed systems have been developed to exploit the energy potential of the gas produced in the exhaust of open combustion turbine systems. See, for example, Van Nostrand's Scientific Encyclopedia 1332-40 (6th ed. 1983), which is hereby incorporated by reference. The reference discloses that in a semi-closed or closed atmospheric air system, energy may be extracted from the exhaust air by a regenerator.
In addition, the reference discloses that in such systems, if a portion of the exhaust air is to be recycled it must be further processed, by a precooler, for example, to change the pressure level, volume, and temperature of the exhaust air to be similar to the pressure level, volume, and temperature of air which enters the closed system at the compressor stage. The reference does not disclose a system or method for processing exhaust steam to change its pressure level, volume, and temperature to be similar to the pressure level, volume, and temperature of steam which enters the closed system at the compressor stage of a system.
In turbine systems, the choice of fuel used in the combustor is important and varies as a function of the type of gas used in the system, i.e., atmospheric air or steam (H.sub.2 O), for example. In atmospheric air systems, natural, refinery, and blast furnace gas are commonly used. In these systems, it is important that the fuel does not form ash which may deposit on the blades or dust which may erode the blades of a turbine and interfere with the long term operation of the turbine.
In semi-closed or closed systems, the choice of fuel is critical because a portion of the gas or air is recycled throughout the turbine system. If the fuel generates ash or dust or other by-products in a semi-closed or closed system, a portion of the by-products will be cycled throughout the entire turbine system with the recycled air. In a semi-closed or closed steam turbine system, ash or dust may adhere to water particles and be transmitted throughout the turbine system. As a consequence, a need exists for steam combustion turbine system which produces little or no byproduct, such as ash or dust, for example, during the combustion process.